Variable configuration jet inlet



Feb. 12, 1957 o. w. NICKS 2,780,913

" VARIABLE CONFIGURATION JET INLET Filed Nov. 30, 1953 2 Sheets-Sheet 2 INVENTOR. ORAN W. NIGKS.

BYW

ATTORNEY tates VARIABLE CONFIGURATION JET INLET Oran-W; Nicks; Inglewood, Califi, assigno'r to North American-Aviafion, Inc.

This invention relates to jet engine inlets and more particularly to an air inlet having variable leading edge configuration.

For-high-s'peed jet-propelled flightgair induction systems having sharp leading edge; inlets provide low drag and go'od pressure recovery characteristics. For'static and low-speed operation, however, these rsharp ed-gedinletsare 'very unsatisfactory because air isbeing' drawn fromall= sidesiand= tends to separate around the sharp leading edge:- The turbulence created bythisyseparation; ineffect; restricts theinlet area, prevents obtaining the desired airflow, and-1'esu|lts-iharedhction in static and take-off thrust; It=is usuallynecessaryto design" sucli an air inlet togive betterperformancefor'staticoperation and hence somewhat lower performance at maximum flight speeds; due-to increased cowl drag; The" must set isfactoryconfignrationfor static and'low speed operation has been found to be* a" blunt or rounded leadingedge which providessmo'oth new WiflilOW'lOSSfiSf and without the above-mentioned separation and turbulence:

The device of this invention contemplatesthe use'of a fluid inlet leading-edge havingvariableconfigurationsoas to he ableito assumesatisfactoryinletcharacteristics-dun ing: both high-speed l andi static and lowsspeedfioperalion.-

It :is -an -object" ofthis -inventionto provide animltrtfor a fluid induction system having good operating; char acteristics laudboth high and. low flnid' -speed-s:

ltristanotherzobject of thisdnventionto provide; for--21 jet engine; an air inletha-ving .good operating characteristics-et both highand" low flight speeds.

It is-another objeet of 'this invention to provide; for a jet engine;.agvariable shape lip inlet havin-ggood -pressure recovery and low drag-at high flight speeds uandi smooth flow; with no separation and low losses.- at low flight speeds.

It.issstillianother-object of this invention toprovidir, for a: jetiengine; .an expandable :lip :inlet having goo'd' pressure recovery characteristics and low drag at high-flightrspeeds and smooth flow with no separation and low losses at low flight speeds:

atent O Fig. 7 isa perspective-view similar to Fig; 6 butshow ingtlre lip expanded and the round leading edge thereof;

Fig. 8 is" a front elevational'view o fan airplanehaving a twoedimensional, variable-shape-lip inlet;

Fig. 9 is a sectionalview taken along line 9-9 of Fig. 8 andshowin'g a modified form of expandable tip for the inlet;

And Big. 10 is'a sectional view similar to Fig. 9 but showing a further. modification of the expandable lip thereof.

In detaiL Fig; 1 shows theinlet cowl, generally desig nated 1, for a conventional jet engine 2.. Inlet cowl 1 is formedwith rigid; sharp. leading. edge or lip 3 sons to provide cowtl .1 with good operating characteristics during flight at high speeds, t0.be later described. Surrounding the exterior of'cowtl land" secured thereto is. expandable boot 4 shown in the inflatedposition in Fig. 1. The deflated position of boot 5 is.shown by the dotted'line at 5, and'the inflation ofbootA'may be caused by. forcing high pressure'fiuid'into the spacev o'between boot 4 and the exterior of cowl 1 through pipe 7 from pressure source or pump 8.

Asshown schematically in Figs. 2; 3 during static and low-speed operation. air is pulledlinto engine 2" through inlet cowl lffrom allsides, In the case of a sharp-edged lip 9' (Fig. I) the incoming-air will tend to separate and form turbulence as at 10; This turbulence restricnsfihe elfective inlet area thereby preventing the engine-from obtaining the desired airflow and resultingreductio-n. in static anditakeoff thrusts. In the. case of a round-edge leading lip 11 (Eig. 3')f the air is drawn infrom all sides and the airflow lines are such that no turbulence and'resuiting effects occur.

At high speeds theoperatingcharacteristics of the two aforementioned inletconfifguratioms are reversed as shown in Figs. 4 and D'urihghigh-speedoperation the sharpedgedlip 9(Eigg 4)" provides low d'rag ,-andgood pressure recovery characteristics Conversely, at hightspeeds the roundeed'ged lip llitFig; 5) gives poor performance bea e ofits increasedxf r a Hence, the;des'irahility,is seen of'vhayingg an inlet cow-l up whose co figl ratiommay be variedito fit all operational 'conditi-ons, Such acowlisshownin Figs. 6yand 7 in perspectivein its deflated *onhigh-speed .operating position and) its inflated or low-speedl operatingepositiong respectively. The device showniinFig. 1,1's particularlyadaptable to a curvate or circular inlet'such as is shown in Figs. 6;;7.

Where the leading lip of an. inlet is substantially traigh fil'i' b lfisinIWQ' lmBD iOnS only,. as is the case Wltli fllfif tria g-ular inlets, shown in F ig. 8, other variable configurationdevices may be employed. The

Other objectstof invention will. become.- apparent from the following description taken inconnection -with;th

accompanying drawings, in which Fig; 1 is an elevational view'of the jet engine inlet partially broken awaytmshow therstructure of the lip constructed in accordance with the preferred form. of. this I sectionahview inFig Q'ShQWsQne of such modifications initgretraetedjorround edged.position; The device of Fig. 9 comprises areciprocable; sharp-edged member 13 underlyingthe outer skinlfdloithe. inlet. Between skin 14': and" member 13 are, a plurality of hiugedlyinterconnected arcuatel'y faced elements 15 which are hingedly connected at one end "toihe forward. end'ofsltin 14andat the other end to operating link 16 whicliis adaptedito' bev actuated by.a hydraulic cylinder 1'7, Elements" l5"and"member-I'3extend the full length of the inlet edges and in the position shown in Fig. 9 elements 15 are positioned so as to provide a continuou rounded lip between the leading edge of skin 14 and the leading edge of member 13 to provide the beneficial static and low-speed operating characteristics previously described.

The shape of the lip thus formed may be changed for high-speed operation by retracting link 16 into cylinder 17, withdrawing element 15 to the dotted line position, and extending member 13 forwardly (as by hydraulic means, not shown) to the position shown by 3 the dot-dash line 18. The lower lip of the inlet shown in Fig. 8 is constructed and operated in the same manner.

In the modification shown in Fig. 10 the fixed portion of the inlet is formed by external and internal skin members 20 21 coming to sharp edge 22. Pivotally connected to sharp edge 22 is one edge of flexible sheet 23 which is bowed'so as to provide a rounded lip. The opposite edge of sheet 23 is pivotally connected to a plurality of three-pivot links 24 which extend rearwardly therefrom. The rearmost pivot 25 of link 24 is secured to block 26 which is adapted to slide on guide 27 between skin members 20 and 21. The intermediate pivot 28 is secured to operating link 29 which is adapted to be withdrawn into hydraulic cylinder 30 upon suitable actuation thereof. When it is desired to change the characteristics of the leading lip from those suitable at static and low-speed operation to those suitable at high-speed operation the withdrawal of link 29 by cylinder 30 will cause link 24 to slide rearwardly thereby pulling sheet 23 to a position overlying sheet 20 and forming a sharpedged lip.

It will be noted that even in the case of a curved-lip inlet the devices shown in Figs. 9 and 10 may be provided in short adjoining or overlapping sections arranged so as to describe the desired inlet shape.

Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the appended claims.

I claim:

1. An inlet for a fluid induction system comprising means forming a constant area inlet having a leading lip, and means for continuously varying the shape of said lip from a sharp edge to a round edge whereby when said lip is sharp-edged it provides low drag and good pressure recovery at high fluid speeds and when said lip is round-edged it provides smooth fluid flow with no separation and low losses at low fluid speeds.

2. An air inlet cowl for a jet engine having good operating characteristics at both high and low flight speeds comprising means forming a constant inlet area having a leading lip, and means for continuously varying the shape of said lip from a sharp edge at high flight speeds to a curvate edge at low flight speeds whereby when said lip is sharp-edged it provides low drag and good pressure recovery at high flight speeds and when said lip is roundedged it provides smooth fluid flow with no separation and low losses at low flight speeds.

3. An air inlet cowl for a jet engine having good operating characteristics at both high and lowflight speeds comprising a leading lip expandable from a sharp edge to a round edge and means for so expanding said lip without decreasing the inlet area of said cowl whereby when said lip is sharp-edged it provides low drag and good pressure recovery at high flight speeds and when said lip is round-edged it provides smooth airflow with no separation and low losses at low flight speeds.

4. An air inlet cowl for a jet engine having good operating characteristics at both high and low flight speeds drag and good pressure recovery at high flight speeds and when said lip is round-edged it provides smooth airflow with no separation and low losses at low flight speeds.

5. An air inlet cowl for a jet engine having good operating characteristics at both high and low flight speeds comprising a curvate sharp-edged leading lip, an expandable, elastic boot surrounding the exterior of said lip, and a source of pressure connected to said boot for expanding said boot to provide a round-edged lip whereby when said lip is sharp-edged it provides low drag and good pressure recovery at high air speeds and when said lip is round-edged it provides smooth airflow with no separation and low losses at low flight speeds.

6. An air inlet cowl for a jet engine having good operating characteristics at both high and low flight speeds comprising a hinged leading lip variable in shape from a sharp edge to a rounded edge and means for so varying the shape of said lip, whereby when said lip is sharp-edged it provides low drag and good pressure recovery at high flight speeds and when said lip is roundedged it provides smooth airflow with no separation and low losses at low flight speeds.

7. An air inlet cowl for a jet engine having good operating characteristics at both high and low flight speeds comprising a hinged-sectioned, rounded lip, a reciprocally mounted sharp-edged lip underlying said rounded lip, means for retracting said rounded lip, and means for extending said sharp-edged lip to a position leading said rounded lip whereby when said sharp-edged lip is leading it provides low drag and good pressure recovery at high flight speeds and when said sharp-edged lip is underlying said rounded lip said rounded lip provides smooth airflow with no separation and low losses at low flight speeds.

8. An air inlet cowl for a jet engine having good operating characteristics at both high and low flight speeds comprising a sharp-edged lip, a flexible, bowed sheet extending from said lip to form a round-edged lip, and means for unbowing and retracting said sheet to a position overlying said sharp-edged lip whereby when said sheet is in said position said sharp-edged lip provides low drag and good pressure recovery at high flight speeds and when said sheet is bowed to form a round-edged lip said roundedged lip provides smooth airflow with no separation and low losses at low flight speeds.

9. An air inlet cowl for a jet engine having good operating characteristics at both high and low flight speeds comprising a sharp-edged lip, a flexible, bowed sheet extending from said lip to form a round-edged lip, a hydraulically operated piston and an associated link for unbowing and retracting said sheet to a position overlying said sharpedged lip whereby when said sheet is in said position said sharp-edged lip provides low drag and good pressure recovery at high flight speeds and when said sheet is bowed to form a round-edged lip said round-edged lip provides smooth airflow with no separation and low losses at low flight speeds.

References Cited in the file of this patent UNITED STATES PATENTS Great Britain Sept. 3, 1948 

